Photo-electric tube



Dec. 10, 1929.

H. E. METCALF PHOTO ELECTRIC TUBE Filed April 16 1925 2 Sheets-Sheet lIN VEN TOR. HERBERT E. METCALFI ATTORNEYS.

1929. H. E. METCALF PHOTO ELECTRIC TUBE Filed A ril'la, 2 Sheets-Sheet 2//\J Wu]. Z

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HERBERT E. METC'ALF'. BY

ATTORNEY-5.

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tread This invention. relates to apparatus iior use in Wireless Wlcommunications and cornniercial use -for rectification, amplihlcagencrat n oi either low high k may oeil y The olo i ct or the inventionis to produce at character employing a vacuum tuhe or i sell having aiihn, layer or surface ve tile material, Whicln under the action oi?light or enternal heat, will cause an emission to the anode so toinaction in the desired manner Without employing the usual hot electrodeinside the tuhe or vessel.

A further ohject ol' the invention is to tacilitate the inanutacture ota rectifier, anr plilier or oscillator at the type mentioned in carryingout these ohjects, ll employ an evacuated vessel oi? glass, quarts, orother suitahle material, which has contained therein a cathode in theterm at a hint, layer or surlace ot a volatile material, such as thesemetals helonging' to the sodium-potassium group connected to the outsideby a suitable connection. This film, layer or surface is deposited bymeans of condensation. There may he contained therein also an anode orcollecting device. The state of the interior of the evacuated vessel mayhe a complete vacuum, or any intermediate stage of gaseous content, orit may be filled after pumping with a gas of the helium group in orderto prevent the breaking down of the cathode.

This device is made so as to function in ractically the same manner asthe wellnown two electrode vacuum tube, except that it shall not containany filament or hot" electrode inside the tube. The emission from theactive and sensitive film, la or or surface is caused either by theaction 0 light fallin upon the cathode or the action of heat applie by aheater. external to the entire tube. It has been found that emission mabe obtained from the cathode to the ano e by the use of either light orheat, and that the emission may be controlled by an intermediateelectrode, if desired, when the anode is kept at a positive potential.It has furthermore beeri found that in the manufacture of such a tubespecial care should be'taken to re'vent the contamination of the anodeby t e subtlun tiled hprll l t lilo. tillltitli'ttt.

stance which is nsedas cathode in order that it inaction properly, andthe present applica tiondiscloses a method whereby such con taininationeliminated.

lln the pre'lerred method of manufacture, the volatile materials, suchas those metals oil the sodiumopotassirun group, are placed on the anodehelore assernhly into the com" plete tuhe, and "when said anode isheated. alter asseinhly into the tuhe, the volatile mas terials thereonare vaporised and deposited. hy condensation on the Walls oi the tube oron a nearhy receptacle tor the purpose at act-'- inp later as a cathode.'lhe cathode material is termed upon the anode and hy means oil heatapplied to the anode, such material is evaporated tol'ornrthe cathode.in this manner the anode is tread train contamination hy the cathodematerial and at the same time the cathode is termed in the shape at afilm deposited over the entire inner ,Wall oil the tuhe or other hase.lln order that the place Where connection is made through the -when-itis set, into operation only in the action' of light, a ortion ofthewalls 0 the tube may be cleans of cathode material by means of heat,thus giving. a ,window whereby light may be admitted to the interior ofthe tube.

In case it is desired that the tube be operated by heatonly, suchawindow is not necessary and the entire tube may he laced inside aheating element which is entirely independent of any electricalconnection to the tube itself. v

In the accompanying drawings- Fig. 1 shows a diagrammatic'view of the.composite filament before the same'is inserted in the vessel or tube.

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Fig. 2 shows a diagrammatic view of the composite filament in placewithin the vessel -or tube and before the same has been heated tube orvessel after the volatile material has been discharged from thecomposite filament and deposited upon the walls of the vessel.

Fig. 5 shows a diagrammatic view of a modified form wherein acylindrical member is placed around the composite filament.

- ig. 6- shows a view of a similar form after the composite filament hasbeen heated to cause deposition of the volatile substance upon thecylinder.

' 7 shows a modified arrangement wherein the volatile material is placedin a reservoir at one end of the vessel and heated by external means tocause deposition of the material u on the walls of the vessel.

Fig. 8 s ows a diagrammatic view of a device embodying my invention andemploying an intermediate member so as to function after-the fashion ofthe well known threeelectrode vacuum tube.

I Referring in detail to Fig. 1 of the accompanying drawings, I show anon-volatile wire 7 upon which there has been deposited a volatileactive substance 8 which is shown merely for clearness in the drawing asbeing in the form of nodules. It may also'be in the form of a smoothcoating. Both ends of this non-volatile wire are brought out with twoterminals 1 and 2. This portion is sealed into 'a vessel 10, as shown inFig. 2. There is a connection 4 on the wall of the tube which willbecome the means for electrical connection to the cathode surface whenit is later formed.

A battery 11 is then attached to the terminals 1 and 2 of thenon-volatile wire, as shown in Fig. 3, and said non-volatile wire 7 isthen heated by the passage of a current. This heat vaporizes thevolatile portion 8 of the wire and such volatile material is depositedin the form of a film 5 over the inside .walls of the tube, as shown inFig. 4, thereby forming the cathode. The cathode is then connectedthrough the medium-of connection 4. This leaves the non-volatile ortionof the entire assembly in 'the center ree of volatile material, asindicated at 6. The two ends 1 and 2 are then joined together to make athird connection 3 which then becomes the anode lead. Referring furtherto Figure 4, it may be seen that the tube is complete, having aconnection 4 to the active cathode surface 5,

- and" a non-volatile wire 6. in the center of the evacuated vesselforming the anode. The surfaces which are not shown covered by cathodematerial have been cleaned of same by heat from an outside source or bythe use of shields during vaporization.

Fig. 5 shows a slightly different type where a metal base is used,whereon the active material is deposited instead of the walls of thevessel 10. This metal base is indicated at 9, being preferably in theform of a cylinder. The procedure for depositing cathode materialthereon is exactly the same as already described. The anode 7 containingcathode material 8 is heated through the medium of the battery '11, asshown in Fig. 6. The active material 8 becoming vaporized is thereupondeposited upon the metal base 9 in the form of an active film or surface5, leaving the center anode 6 free and uncontaminated from cathodematerial.

Fig. 7 shows a device of this sort which is made by the vaporization ofactive material from an outside well 8. This active material may bevaporized by the application of external heat and is deposited bycondensation in the form of a film 5 on the walls of a vessel llO, thecathode connection being made at 4.

However, in making a device of this sort it is difiicult to prevent theanode 6 from being contaminated by condensed cathode material, so bymaking the anode 6 in the form of a loop or continuous wire, both endsbeing brought to the outside, the current from the attery 11 may bepassed through the anode terminals 1 and 2, heating the anode 6, therebyevaporating from it and cleansing it of all cathode contamination.

Fig. 8 discloses a method whereby an intermediate member may beintroduced into this evacuated vessel 10. Either or both the member 15and anode 6 may be used to deposit the volatile active material.However, it is important that a current be passed through both the anodeand the intermediate member 6 and 15, so that they may be efl'ectivelycleansed of contamination by cathode material. For this purpose I showbatteries 11 and 13. The evacuated vessel in this case would actpractically in the same manner as the well known three-electrode vacuumtube.

Various changes in the construction and arrangement of the several partsherein shown and described may be employed without departing from thespirit of my invention as disclosed in the ap ended claim.

Having thus descri (I my invention what I claim and desire to secure byLetters Fatent 1s:

In a two-electrode vacuum tube having an evacuated vessel and doubleterminal anode, the latter having deposited thereon a volatile materialsensitive to the action of light, the step of heating the anode to causethe volatile material to be vaporized and deposited in the form of asensitive film upon the inner wall of the vessel, whereby to form alight sensitive cathode.

HERBERT E. METCALF.

